1. Field of the Invention
The present invention relates to a chemical amplification type positive resist composition used in fine processing of semiconductors and also provides a novel resin useful for the resist composition.
2. Related Art
Semiconductor microfabrication employs a lithography process using a resist composition. In lithography, theoretically, the shorter the exposure wavelength becomes, the higher the resolution can be made, as expressed by Rayleigh's diffraction limit formula. The wavelength of an exposure light source for lithography used in the manufacture of semiconductor devices has been shortened year by year as g line having a wavelength of 436 nm, i line having a wavelength of 365 nm, KrF excimer laser having a wavelength of 248 nm and ArF excimer laser having a wavelength of 193 nm. F2 excimer laser having a wavelength of 157 nm seems to be promising as the next-generation exposure light source. Further, as the exposure light source of the subsequent generation, soft X ray (EUV) having a wavelength of 13 nm or shorter has been proposed as the exposure light source following the 157 nm-wavelength F2 excimer laser.
Since light sources having shorter wavelength than that of g line and i line, such as excimer laser and the like have low illumination, it is necessary to enhance the sensitivity of a resist. Consequently, there are used so-called chemical amplification type resists utilizing the catalytic action of an acid produced from a sulfonium salt and the like by exposure and containing a resin having a group being dissociated by this acid (JP2000-137327 A).
For further reduction of exposure time, chemical amplification type resist composition is required to have higher sensitivity than conventionally known compositions.